In an apparent effort to prevent the transformation of Central Square into Times Square, advertisement billboards will be outlawed in Cambridge starting Saturday.

A city ordinance passed in 1991 takes effect April 10, and City Manager Robert W. Healy will begin enforcing the ban on the city's 52 billboards.

But residents should not expect the billboards--including one atop the Wursthaus in Harvard Square--to disappear anytime soon. Ackerley Outdoor Advertising, which owns 47 of the 52 billboards, is preparing a legal challenge to the ordinance.

"They're trying to suffocate First Amendment speech, my right to make a statement on structures we own," said Louis R. Nickinello, president of Ackerley Outdoor Advertising, based in Stoneham. "They're strictly trying to discriminate against us."

But the City Council, which passed the 1991 law, disagreed. Calling advertisements urban nuisances and an eyesore, the council gave Ackerley and the Revere-based Rite Media Inc., which owns the other five billboards, four years to remove them.

Of Ackerley's billboards, 36 are 12 by 25 feet and 11 are 14 by 48 feet. Rite Media's billboards are all 14 by 48 feet in size.

At Monday's City Council meeting, several Cantabrigians voiced support for a motion by Councillor Katherine Triantafillou to enforce the law immediately.

"We're on the third floor of a triple-decker and we can't see the sky for much of the year," John Nachazel told the council. "Nobody is in favor of the billboards. I hope that you will enforce the ordinance that you in your wisdom have passed."

Other residents contend the bill- boards are not only esthetically displeasingbut damaging to the infrastructure of buildings.

Architect W. Easley Hamner said the HarvardSquare billboard has damaged the building below itthrough its structural supports. "It's almostliterally torn those buildings apart beneath it,"Hamner said.

Since the passage of the 1991 ordinanceAckerley has stopped using the billboards forcommercial ads, instead donating the space forpublic service announcements or using the boardsfor non-commercial speech. Four years ago, itstarted a "quote campaign," with aphorisms byluminaries such as Albert Einstein and the Rev.Dr. Martin Luther King Jr.

"Kindness is the golden chain by which asociety is bound together" reads one ad, quotingEinstein.

But some residents interpret the move as acynical public-relations tactic designed to stifleopposition to the boards.

"They block out what should be a prime focalpoint of our square," said Lansing Fair, an InmanSquare resident. "[The quotes] are cynicalproverbs designed to be read in a vacuum of publicsupport."

Nickinello, however, said the billboards werein fact serving a public good.

"I decided to do some inspirational andpositive quotes and bring back some statementsmade by famous people and remind people that thereare some good things in this world," he said.